Research On Fatigue Life Of Bucket Rod Of Hydraulic Excavator

Hydraulic excavator is an important construction machinery,widely used in the national economic construction.The working device is constantly subjected to the alternating load and impact load due to the varied working condition and the bad working environment in its operation.So the problems of fatigue fracture often occur.This paper is based on the National Science and Technology Support Project“Research on the generic technology of energy conservation and emissions reduction of construction machinery”?Item no.:2015BAF07B01?.It takes a medium hydraulic excavator as the study subject,uses the nominal stress method and the nonlinear cumulative damage theory to predict fatigue life of the bucket rod of this type excavator.The main contents of this paper are as follows:?1?The mechanical analysis of the working device is carried out,and the relation between the joint load of bucket rod and the force of hydraulic cylinder is obtained.The finite element analysis is carried out on the bucket rod under four dangerous conditions,the stress clouds of the bucket rod are obtained.And the fatigue risk area of the bucket rod is determined.?2?The dynamic load test including 3 working objects?soil,rock,soil and rock mixture?is carried out.The strain time history of the 52 strain gauges distributed around the bucket rod is obtained.The pressure time history of large and small cavity and the displace time history of hydraulic cylinder are also got.Through the mechanical analysis of the working device,the joint load time history of the bucket rod is obtained.?3?The dynamic simulation of excavator in operation is carried out.The stress time history of the fatigue risk area on the bucket rod is obtained.Referring to the IIW standard of the International Welding Association,the S-N curve of the bucket rod is determined.A fatigue life prediction method based on counting cycle is proposed to deal with the cumulative damage.The square of the two consecutive stress ratio??₂/?₁?² is used to perform the effects of load interaction.A new nonlinear cumulative damage theory considering the effects of load interaction is put forward,and the rationality of the method is verified by the experiment.?4?The fatigue life of the bucket rod is predicted by the proposed method.The structure of the bucket rod is improved.The feasibility of the improving structure is proved from two aspects of finite element analysis and fatigue life prediction.